This invention relates to a typewriter with an erasing apparatus capable of consecutively erasing a series of characters once printed on a sheet of printing paper.
A British Pat. No. 1,316,534 discloses a method of and apparatus for removing printed characters from a printing paper on which they have been printed by means of striking an erase ribbon having an adhesive surface on those printed characters. In this apparatus the characters have to be erased or removed by the same printing mechanism that has been used in the printing thereof.
In a typewriter provided with this erasing apparatus an erasing operation is carried out in the following manner when, for example, a printed character "H" is required to be erased.
A carriage of the typewriter is first of all spaced backwards by one character-size increment so as to set the next print position over the place where the character "H" has been printed, and at the same time or immediately thereafter the erase ribbon is so preset as to be ready for being lifted from an original position to a print position according to one character printing operation in a printing mechanism, just like a character printing ribbon such as an ink ribbon used in ordinary printing operations. A type "H" is then struck by the printing mechanism on the printed "H" via the erase ribbon.
In the ordinary printing operation every motion of the printing mechanism is delivered to a carriage driving mechanism upon printing of each character so as to advance the carriage by one character-size increment. When, however, the erasing apparatus is operated the printing mechanism is so preset as not to deliver the movement thereof to the carriage driving mechanism simultaneously with the preset of the erase ribbon. Consequently, the carriage is restricted to move even after the termination of the erasing operation.
Such a preset state is however released by the execution of the erasing operation, which allows the printing mechanism to print a new or correct character on the erased place when it is worked after the erasion. The carriage is then allowed to advance by one character-size increment.
In a typewriter having such an erasing apparatus an operator is obliged, when he or she consecutively erase or correct a series of characters, to space the carriage backwards and to preset the erase ribbon and a mechanism for non-escapement at each erasion of one character. This causes the erasing operation to be very complicated and troublesome.